In many surgical spinal procedures, such as the correction of scoliosis, nerve root decompression, interbody fusion, tumor removal, repair of kyphosis, and treatment of other spinal defects or trauma, it may be desirable or necessary to supply forces by compression and/or distraction to vertebrae in a defective region. In some cases, the defective region includes lordotic curvature. The defective region may also include multiple levels of vertebrae. In some cases, one of the levels of the spine must be skipped during the compression and/or distraction procedures.
Typically, bone screws, e.g., medical screws, are inserted into the vertebrae of the defective region and spinal rods are used to rigidly fix the vertebrae relative to one another. In particular, bone screws include a shaft and a screw head having a pair of sidewalls extending upwardly and spaced apart from each other so as to form a channel. The channel is configured to receive the spinal rod in a manner such that the axial length of the spinal rod extends between at least two adjacent vertebral bodies. The shaft is typically threaded so as to find purchase in the vertebral body, wherein the screw head is exposed and the channel is positioned to receive the spinal rod. Current compression tools as depicted in FIG. 1 typically include a pair of legs 1 that attach onto the pair of side walls of bone. A compression force as shown by arrows 3 is applied to the legs 1 which in turn results in compression of the spine, i.e., the pair of bone screw assemblies 300 are moved closer to each such that the distance between the pair of vertebrae decreases. The bones screw assemblies 300 may be referenced herein generally as 300 and with particularity as 300a, 300b, 300c, and 300d. Such compression tools subject the screw head assemblies, in particular the sidewalls, and the bone screw assemblies 300 to external forces which may be undesirable, i.e., the compression force is applied directly to the bone screw assemblies 300 and particularly to the heads of the bone screw assemblies 300.
In addition, the fixed attachment of the legs 1 to the screw head assemblies of the bone screw assemblies 300 engages the screw head by pushing on the sidewalls as the legs are brought together. Such a configuration does not allow or provide for pivoting or rotation between the legs 1 and the screw head assemblies of the bone screw assemblies 300 such that the compression force may compress the vertebrae of the spine along a desired curvature of the spine.
Obtaining the desired spatial relationship between vertebrae is achieved by using two tools; each tool is coupled to a pair of bone screws. The pair of bone screws is disposed on opposite sides of the vertebral body. Once the desired spatial relationship of the vertebrae is obtained by each of the tools, one tool is released and the rod is inserted into the channels of the open bone screw and the bone screw is fixed to the rod by use of a fastening device such as a set screw. The set screw is configured to threadingly engage the threaded sidewalls and tighten onto the spinal rod. Once one side of the vertebral bodies are secured vis-à-vis the fixation of the bone screws to the spinal rod, the other tool is released and the other side of the vertebral bodies are secured in position with each other in a like manner.
Current tools are fitted onto the screw heads and thus are disposed directly above the surgical site, taking up operating space. Accordingly, it also remains desirable to have a tool which may be manipulated so as to be clear of the operating space without being disengaged from the bone screws so as to maintain the desired spatial relationship while the rod is being fixed to the bone screws.